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| Home > Publications database > Neuartiges Herstellungsverfahren für kohlenstofffaserverstärktes Siliziumcarbid mit faserdominiertem Verhalten |
| Dissertation / PhD Thesis/Book | PreJuSER-38312 |
2003
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/298
Report No.: Juel-4094
Abstract: In order to use ceramics as structural materials their damage tolerance must be increased, which can be achieved by fiber reinforcement. This thesis deals with one of the most important representatives of these fiber-reinforced ceramics - carbon-fiber-reinforced silicon carbide (C/SiC). Liquid silicon infiltration is an established process for manufacturing C/SiC. A porous substrate of carbon-fiber-reinforced carbon (C/C) is infiltrated by liquid silicon, which should react mainly with the carbon material of the matrix to form silicon carbide. In fact, it also reacts with the carbon fibers, which thus are decisively affected. Therefore, a high content of residual carbon within the matrix is generally included (so-called C/C-SiC) to ensure sufficiently high damage tolerance. The objective of this thesis was the development of a new or modified processing route based on liquid silicon infiltration. In doing so, primarily the drawback of fiber attack was to be avoided even though the matrix is completely changed into silicon carbide while retaining the advantages of an inexpensive and simple processing route. In the manufacturing method developed, the silicon is added at the outset, uniformly distributed within the matrix. Thus it can react in situ with the surrounding carbon of the matrix to form silicon carbide. The reaction is essentially limited to the matrix and the fiber attack is minimized. A uniform and highly porous matrix is formed with small pore radii. In contrast to liquid silicon infiltration, there is no remaining free silicon. The highly porous matrix effects that a fiber-dominated material is obtained - a group of fiber-reinforced ceramics that has been little analyzed as yet. Stiffness as well as strength is determined by the fibers. The aim of activating mechanisms to attain a damage-tolerant fracture behavior is achieved. The properties of the C/SiC material developed here equal the performance data of liquid-silicon-infiltrated material with a high content of carbon within the matrix (C/C-SiC), even if the matrix is completely converted into silicon carbide. They only lag behind high-quality and expensive commercial high-performance materials with the more conventional weak fiber-matrix interface due to fiber coatings. The efforts and costs involved in the new process are regarded as comparable to liquid silicon infiltration. Thus the material - with a different spectrum of properties - is close to introduction as an industrial structural material apart from aerospace applications.
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